This invention relates to the field of integrated circuit fabrication. More particularly this invention relates to a system for performing contaminant sensitive processing on a substrate.
A variety of different materials are typically used in integrated circuit fabrication processes. Many of these materials are highly susceptible to various contaminants. In addition, some processes, at intermediate points, create sites or structures that are very susceptible to contamination. For example, when trenches or holes are etched into dielectric films, the dielectric films tend to be extremely susceptible to contaminants in the atmosphere such as oxygen, nitrogen, rare gases, hydrocarbons, water vapor and other atmospheric contaminants. When exposed to such, the etched portions of the dielectric layer tend to attract such contaminants.
In the specific case of low dielectric constant materials, which tend to be porous in nature, the adsorption of contaminants tends to be even greater. Thus, when a low dielectric constant material is etched, the etched portions tend to adsorb contaminants. Then, when a thin material layer is subsequently deposited over the etched portions, such as when a diffusion barrier is formed in a via, the contaminants absorbed in the low dielectric constant material in the area of the etched via tend to outgas and interfere with the uniform and desirable deposition of the deposited layer. This condition tends to cause problems with the integrated circuit, such as barrier layers that are porous or otherwise defection, and which do not exhibit the desired barrier properties.
As a more specific example, when a titanium adhesion layer is deposited in an etched silicon oxide via, and then the titanium adhesion layer is followed by a titanium nitride diffusion barrier layer, and then the titanium nitride diffusion barrier layer is followed by a tungsten plug deposition, the resultant structure often exhibits a breakdown of the barrier diffusion layer, which is typically referred to as poisoned vias or poisoned plugs.
What is needed, therefore, is a system for forming structures on a substrate, where the substrate and the various layers are not exposed to a contaminant laden environment.
The above and other needs are met by an apparatus for performing contaminant sensitive processing on a substrate. A substrate load chamber receives the substrate from an ambient contaminant laden environment, and isolates the substrate from the ambient contaminant laden environment. The substrate load chamber further forms a first environment of intermediate cleanliness around the substrate.
A substrate pass through chamber receives the substrate from the substrate load chamber, and isolates the substrate from the intermediate cleanliness of the first environment of the substrate load chamber. The substrate pass through chamber further forms a second environment of high cleanliness around the substrate.
A substrate transfer chamber receives the substrate from the substrate pass through chamber, and isolates the substrate from the high cleanliness of the second environment of the substrate pass through chamber. The substrate transfer chamber maintains a third environment of high cleanliness around the substrate, and transfers the substrate into more than one substrate processing chambers, where the substrate is selectively transferred into and out of the more than one substrate processing chambers without leaving the high cleanliness of the third environment.
The substrate transfer chamber also selectively passes the substrate to the substrate pass through chamber when the substrate pass through chamber has formed the high cleanliness of the second environment. The substrate pass through chamber also receives the substrate from the substrate transfer chamber, and selectively passes the substrate to the substrate load chamber when the substrate load chamber has formed the intermediate cleanliness of the first environment. The substrate load chamber receives the substrate from the substrate pass through chamber, and selectively passes the substrate out of the substrate load chamber and into the ambient contaminant laden environment when the substrate load chamber is not open to the substrate pass through chamber.
Because there is a substrate pass through chamber between the substrate load chamber and the substrate transfer chamber, the high cleanliness environment of the substrate transfer chamber is never exposed to the intermediate cleanliness of the substrate load chamber, or the contaminant laden ambient environment. Thus, the substrate pass through chamber, by forming an environment of high cleanliness before transferring a substrate to or accepting a substrate from the substrate transfer chamber, protects and helps maintain the high cleanliness of the environment of the substrate transfer chamber. Therefore, those contaminant sensitive processes that are performed in the various substrate processing chambers are not exposed to the environment of intermediate cleanliness or to the contaminant laden ambient environment, and the intermediate structures which may be created by these various processes are likewise not exposed to the environments of lesser cleanliness.
In another aspect of the invention, a method of performing contaminant sensitive processing on a substrate is given. The substrate is transferred from an ambient contaminant laden environment and into a substrate load chamber. The substrate is isolated from the ambient contaminant laden environment with the substrate load chamber, and the substrate load chamber forms a first environment of intermediate cleanliness around the substrate.
The substrate is transferred from the intermediate cleanliness of the first environment of the substrate load chamber and into a substrate pass through chamber, where the substrate is isolated from the intermediate cleanliness of the first environment of the substrate load chamber. A second environment of high cleanliness is formed around the substrate with the substrate pass through chamber.
The substrate is transferred from the high cleanliness of the second environment of the substrate pass through chamber and into a substrate transfer chamber, where a third environment of high cleanliness is maintained around the substrate. The substrate is selectively transferred into more than one substrate processing chambers, where the substrate is selectively transferred into and out of the more than one substrate processing chambers without leaving the high cleanliness of the third environment. The substrate is selectively processed in the more than one substrate processing chambers.
The substrate is transferred to the substrate pass through chamber from the substrate transfer chamber when the substrate pass through chamber has formed the high cleanliness of the second environment and the substrate pass through chamber is not open to the substrate load chamber. The substrate is transferred to the substrate load chamber from the substrate pass through chamber when the substrate load chamber has formed the intermediate cleanliness of the first environment and the substrate pass through chamber is not open to the substrate transfer chamber. The substrate is transferred out of the substrate load chamber and into the ambient contaminant laden environment when the substrate load chamber is not open to the substrate pass through chamber.